What's inside my distribution board?
Open the panel door and you'll see a row of switches with no explanation attached. This guide explains, in plain language, what each device actually does -- no installation or testing instructions included. Recognising the devices is useful for any homeowner, but replacing them stays a licensed electrician's job.
How to use this guide
Look, don't touch
You can open the panel door to look at the devices, but the internal wiring and terminals aren't a DIY zone -- that's licensed electrician territory.
Recognise the device category
Each device usually carries markings or a symbol on its front that show its type -- enough to know roughly what you're looking at, even without technical detail.
Understand what it does
This page explains what each device category does in plain terms -- without technical ratings, which are always project-specific anyway.
Know where DIY ends
Identifying a device is safe and useful. Replacing, adding, or testing one isn't -- that always needs a licensed electrician.
Devices you'll commonly find
4 core device roles
Most distribution boards contain these basic categories, each with a clearly separate function.
MCB -- miniature circuit breaker
Protects a circuit against overload and short circuit -- it trips when too much current flows through it.
RCD -- residual current device
A standalone device that protects against earth leakage current, for example from damaged insulation -- no overload function.
RCBO -- both functions in one
Combines circuit breaker and RCD functions in a single unit -- overload and leakage protection together.
SPD -- surge protection device
Protects sensitive electronics from brief overvoltages, for example the indirect effects of lightning.
Main incomer switch
Lets you cut power to the whole board at once -- usually the largest device, near the start of the row or the meter.
What a consultation includes
Want more clarity about your specific board? We can talk it through one-on-one.
- A review of your existing distribution board
- Plain-language explanation of each device's role
- An honest opinion on whether anything needs attention
- A link to full installation or inspection services
- No sales pressure
Frequently asked questions
Can I replace an MCB myself?
Identifying devices is safe for anyone, but replacing one or working inside the board is licensed electrician's work.
What's the difference between RCD and RCBO?
An RCD protects only against leakage current, while an RCBO combines leakage and overload protection in one unit.
Is an SPD required in every board?
That depends on the project and the applicable standard -- best checked with your designer or electrician.
What does the IP rating on the enclosure mean?
The IP rating (for example IP44) describes resistance to dust and water -- the required class depends on the installation environment.
Why do some homes have several RCDs and others just one?
The type and number of devices is chosen at the design stage based on the circuit layout and the property -- there's no single fixed rule.
Not sure what's what in your board?
Book a consultation -- we'll talk through your specific distribution board, no sales pressure.